Spectral sensitization of photographic emulsions

Abstract

Photographic emulsions are sensitized to the red region of the spectrum with a combination of three sensitizing dyes. The dyes have the generic structural formulae: ##STR1##

What is claimed is: 
     
       1. A photographic silver halide emulsion sensitized to the region of the electromagnetic spectrum between 590 and 640 nanometers with a dye from each of the following groups I, II and III: I. a dye having the structural formula: ##STR16##  where: Y is selenium or sulfur; Z is oxygen or ##STR17## R is methyl or ethyl; R 1  and R 2  are each acid substituted alkyl;   α is hydrogen;   G is hydrogen;   G 1  is hydrogen, halogen or alkoxy;   G 2  is hydrogen or alkoxy; or   G and G 1  or G 1  and G 2  are the atoms necessary to complete a fused benzene ring;   G 3  is alkyl, alkoxy, aryl, halogen or styryl; and   G 4  is hydrogen, alkyl or halogen;     II. a dye having the structural formula: ##STR18##  where: R is methyl or ethyl, R 1  and R 2  are each hydroxyalkyl or each acid-substituted alkyl; and   G 1  and G 2  are, independently, hydrogen, halogen, alkyl, aryl or alkoxy, provided that at least one of G 1  and G 2  is a substituent other than hydrogen; and     III. a dye having the structural formula: ##STR19##  where: R is methyl, ethyl or a negatively charged ketomethylene residue which forms an allopolarcyanine dye; and R 1  and R 2  are each acid-substituted alkyl; and dyes I, II and III have associated an anion or a cation, if necessary to neutralize the charge on the dye molecule.     
     
     
       2. A photographic emulsion of claim 1 wherein; in formula I, Y is sulfur, R is ethyl, R 1  and R 2  are sulfoalkyl, α is hydrogen, G is hydrogen, G 1  and G 2  are hydrogen or alkoxy, G 3  is alkyl or aryl and G 4  is hydrogen; in formula II, R is methyl or ethyl, R 1  and R 2  are each hydroxyalkyl or each sulfoalkyl and G 1  and G 2  are alkoxy; and in formula III, R is methyl or ethyl and R 1  and R 2  are sulfoalkyl. 
     
     
       3. A photographic emulsion of claim 1, wherein: in formula I, Y is sulfur, R is ethyl, R 1  and R 2  are sulfoalkyl, α is hydrogen, G is hydrogen, G 1  and G 2  are alkoxy, G 3  is phenyl and G 4  is hydrogen; in formula II, R is ethyl, R 1  and R 2  are hydroxyalkyl and G 1  and G 2  are alkoxy; and in formula III, R is ethyl and R 1  and R 2  are sulfoalkyl. 
     
     
       4. A photographic emulsion of claim 1, wherein the dyes of formulae I and II are present in an amount of about 0.05 to 0.5 millimole of dye per mole of silver halide and the dye of formula III is present in an amount of about 0.01 to 0.05 millimole of dye per mole of silver halide. 
     
     
       5. A photographic element comprising a support bearing a layer of the emulsion of claim 1. 
     
     
       6. A photographic element comprising a support bearing a layer of the emulsion of claim 2. 
     
     
       7. A photographic element comprising a support bearing a layer of the emulsion of claim 3. 
     
     
       8. A photographic element of claim 5, wherein the emulsion layer is one of the layers in a multilayer, multicolor photographic element. 
     
     
       9. A photographic element of claim 7, wherein the emulsion layer is one of the layers in a multilayer, multicolor photographic element. 
     
     
       10. A photographic element of claim 8, wherein the emulsion layer has associated with it a color coupler. 
     
     
       11. A photographic element of claim 10, wherein the color coupler is a cyan dye producing color coupler.